There are 2 different type of challenge.
A Story mode with 4 different levels. Each level has a big boss at the end.
A survival mode where you have to kill as much enemies as you can.
The system will put on the Menu page the top record.
You can play with one or two players.. it is possible to join a game when only one player is playing. Also if a player is dead you can continue by adding new coins.
Enjoy it!!!